1. Field of the Invention
This invention relates generally to aircraft systems, and more particularly to aircraft systems that may be used for aerial dispersion of materials.
2. Description of the Related Art
Aircraft are commonly employed for the aerial dispersion of liquid and/or solid materials such as fire retardant or fire extinguishing materials, oil dispersant materials, bio-remediation materials, fertilizer materials, herbicide materials, defoliant materials, pesticide materials, etc. For example, specially-equipped aircraft are used to carry and deliver fire retardant materials to the area of a forest or brush fire. Such fire-fighting aircraft are typically converted World War II era bombers or propeller-driven passenger or cargo planes that have a carrying capacity limited to 3000 gallons or less of liquid fire retardant material. These vintage aircraft typically deliver their load of fire retardant material by flying to the area of the fire and then making a low altitude bombing run over the fire that often requires steep dives and climbs to accurately deliver the fire retardant payload to a targeted fire hot spot. The nature of these low altitude bombing runs often result in g-force stresses that exceed the structural rating of these aircraft, weakening the structure of the aircraft and in some cases causing in-flight structural failures leading to loss of the aircraft and crew. A limited supply of vintage aircraft and the grounding of particular types of aircraft due to structural weaknesses has resulted in a shortage of fire-fighting aircraft.
Many vintage aircraft are converted for aerial dispersion of materials by the permanent installation of material dispersion equipment. Modular aerial spraying systems have also been developed for use in conversion of C-130 cargo aircraft for aerial spraying purposes. Known as the Modular Airborne Fire Fighting System (“MAFFS”), these systems employ portable pressurized tanks which are loaded onto a C-130 aircraft through the lowered rear cargo ramp of the aircraft. The lifting capacity of the C-130 aircraft limits the amount of water or water-based retardant which may be carried by the MAFFS aircraft to about 3000 gallons. Most MAFFS are “single shot” systems that discharge a full 3000 gallon load at one time, although there exist two load MAFFS units that may split a 3000 gallon load into two separate discharges. Because of their drop pattern, MAFFS are not typically used for support in residential areas or for initial attack on a fire, which usually require multiple drops from a single air tanker. In addition to limitations in MAFFS capacity and drop pattern, certain C-130 aircraft that are employed for MAFFS purposes have been recently grounded due to excessive stresses imparted on these aircraft when using them for aerial fire-fighting.
Specialized modern aircraft have also been developed for aerial fire-fighting purposes. In this regard, the Canadair CL-415 is capable of in-flight re-filling from large bodies of water, such as lakes. However, the CL-415 is very expensive relative to vintage aircraft, has a limited carrying capacity of approximately 1621 gallons of liquid fire retardant material, and the cost of obtaining and maintaining a state-of-the-art modern fleet of such aircraft would be prohibitive. Furthermore, such a fleet of fire-fighting capable aircraft is not needed all the time. Thus, the relatively small carrying capacity, specialized nature, and high cost of such aircraft prohibits large-scale deployment in an aerial fire-fighting fleet.
Further information on practices and condition of the aerial firefighting fleet in the United States may be found in Federal Aerial Firefighting: Assessing Safety and Effectiveness, Blue Ribbon Panel Report to the Chief, USDA Forest Service and Director, USDI Bureau of Land Management, December 2002.